Impact of Signal Timing Information on Safety and Efficiency of Signalized Intersections

Signalized intersections are provided in traffic networks to improve the safety and efficiency of vehicular and pedestrian movement. There are various measures under education, enforcement and engineering headings that are being attempted to improve safety and efficiency of operations at a signalized intersection. Provision of signal countdown timer, a timer showing the remaining red and green time in a phase, is one such measure and is commonly adopted in India. However, studies on effects of countdown timer under Indian traffic conditions are very scarce. Traffic heterogeneity and lack of lane discipline makes transferability of models developed in other countries (with more organized traffic) infeasible. The present study is an attempt to analyze the changes in queue discharge characteristics and red light violations (RLV) under Indian traffic conditions due to the presence of timer. A before and after analysis was carried out using the data collected from a selected intersection in Chennai, India. The analysis is carried out for different vehicle types in the presence and absence of timers separately for the start and end of red/green. Results showed that the information provided at the start of green (end of red) enhances efficiency, the startup lost time is reduced and there is an increase in red light violations. Two wheelers present at the start of the queue are found to be the category that is mostly affected by this information. However, the information provided at end of green (start of red) was found to reduce the red light violations. In the presence of information, it was found that the 1 Assistant Professor, University of Nebraska Lincoln, Department of Civil Engineering, Nebraska Hall W348 Lincoln, NE 68588-0531;Phone: (402) 472-6391;E-mail: [email protected] 2 Corresponding Author, Assistant Professor, Department of Civil Engineering, Indian Institute of Technology Madras, Chennai 600 036, INDIA; Phone: 91 44 2257 4291;E-mail: [email protected] 3 Former Masters student, Department of Civil Engineering, Indian Institute of Technology Madras, Chennai 600 036 4 Undergraduate student, Department of Civil Engineering, National Institute of Technology Calicut, INDIA Sharma, Vanajakshi, Girish & Harshitha in Journal of Transportation Engineering (April 2012) 138: 467-478. Copyright 2012, ASCE. Used by permission.